With prior art telephony systems, if a user of a telephone in an organisation having a switch configured above wishes to establish, say, an outgoing call, and all outgoing lines are currently fully utilised, that user will have to wait until an outgoing line or sufficient outgoing capacity is available. Similarly, if a third party wishes to call that user and all of the incoming lines to that organisation are busy, that third party would have to wait until an incoming line is available.
The same situation may arise with any communication system which has a limited bandwidth over which information or data can be transmitted. For example, with a multi-media computer capable of generating a plurality of information media types, such as video, data or sound, if there is insufficient outgoing capacity to support a communication link between, say, two such computers used for collaborative or group working, then users of those computers will have to wait until sufficient outgoing capacity to support communication therebetween is available.
Another concern that has arisen is the asymmetric nature of telephone costs. In other words, the price of a call of a given length between A and B may depend on whether A initially dialled B, or vice versa. These differences tend to be particularly significant for international calls, but may also exist for example where the parties are very disparate in size, and one has negotiated a discounted rate in view of its high volume of calls. However, it has been very difficult in the past to be able to exploit such charging differences in order to minimise call costs.
A further concern is that tariff charges vary depending on the telephone provider as well as on the country from which the call is initiated and when the call is made. Previously, in the majority of countries where there is limited or no competition, enterprises have been forced to buy international telephone calls at fixed tariffs offered by local suppliers and as a result providers have been making excess profits from international calls. However there now exist alternative network providers or agencies which buy international telephone capacity in bulk and sell it at a discount. Users can call the local offices of the agency who then set up the call over the agency's network and call the user back when the connection is made. Unfortunately this manual process is tedious and discourages users. Other agencies re-sell their bulk purchased capacity by updating the call routing tables in the user's telephone switch. This can be very time consuming as the agency has to manually reprogram the call routing tables and has a further disadvantage that the user is still closely tied to a single agency or network provider.